Sheet metal punching apparatus and method thereof

ABSTRACT

A sheet metal punching apparatus  1  includes an upper die holder  2  which is raised and lowered by a hydraulic ram and the like; a pressing plate  3  secured to the upper die holder  2 ; a pressing pad  5  suspended from the upper die holder  2  through a resilient member  4 ; a punch holder  7  secured to the pressing pad  5  by means of a bolt  6  and the like and constructed as a punch unit; a lower die  9  on which a sheet metal  8  to be subjected to punching is placed; and a die  11  embedded in the lower die  9  and having a though hole  10  of an oval shape conforming to the shape of a through hole to be punched in the sheet metal  8.

TECHNICAL FIELD

The present invention relates to a sheet metal punching apparatus and a method thereof.

BACKGROUND ART

-   [Patent Document 1] JP-A-2005-262263 -   [Patent Document 2] JP-A-2002-153920

DISCLOSURE OF THE INVENTION Problems that the Invention is to Solve

An apparatus for punching a hole in a sheet metal is arranged such that a punch having an outside diameter smaller than the diameter of a through hole of a die is pressed against a sheet metal, and the punch is further inserted into the through hole of the die to cause a shear to occur in the sheet metal through cooperation between the punch and die, thereby forming in the sheet metal a through hole of a configuration conforming to the configuration of the through hole of the die.

Incidentally, for the purpose of punching a circular through hole in a sheet metal, a punch whose outer configuration has a circular shape similar thereto is commercially available as a standard item and is easily obtainable. However, for the purpose of punching a through hole of a special configuration other than the circular shape, it is difficult to obtain a punch whose outer configuration is similar thereto as a standard item, and the present situation is such that a punch conforming to the through hole of the special configuration is fabricated by a special order. Such a punch inevitably becomes expensive, and there is a problem in that a punching processor must constantly keep expensive punches of the special configuration prepared as reserves.

The present invention has been devised in view of the above-described aspects, and its object is to provide a sheet metal punching apparatus and a method thereof which make it possible to effect punching of a through hole of a special configuration other than the circular shape without using a punch whose outer configuration is similar thereto, thereby making it possible to attain a reduction in the punching cost.

Means for Solving the Problems

A sheet metal punching apparatus in accordance with the present invention comprises: a die having a through hole of a configuration conforming to a configuration of a through hole to be formed in a sheet metal; and a punch means including a punch body means having an outer configuration dissimilar to a configuration of an outer edge of the through hole of the die and adapted to form a through hole in the sheet metal in cooperation with the die and a pierced hole forming means which is integrally provided on one end face of the punch body means facing the through hole of the die and is adapted to form a pierced hole in the sheet metal, wherein the pierced hole is formed in the sheet metal by the pierced hole forming means, and in a state in which the movement of the sheet metal is restricted by the pierced hole forming means inserted in the pierced hole, the punch body means is inserted into the through hole of the die, whereby the sheet metal is subjected to tensile fracture at the outer edge of the through hole of the die through cooperation between the die and the punch body means, to thereby form the through hole in the sheet metal.

According to the above-described sheet metal punching apparatus, the pierced hole is formed in the sheet metal by the pierced hole forming means, and in the state in which the movement of the sheet metal is restricted by the pierced hole forming means inserted in the pierced hole, the punch body means having an outer configuration dissimilar to the configuration of the outer edge of the through hole of the die is inserted into the through hole of the die. Thereupon, the sheet metal is subjected to tensile fracture at the outer edge of the through hole of the die through cooperation between the die and the punch body means, to thereby form the through hole in the sheet metal. Therefore, it is possible to effect punching by using the punch whose outer configuration is circular or quadrangular in shape without using a punch whose outer configuration is similar to that of the through hole to be punched, thereby making it possible to attain a reduction in the punching cost.

In the punching apparatus of the present invention, the punch body means may have at least one punch body having an outer configuration dissimilar to the configuration of the outer edge of the through hole of the die. In this case, the pierced hole forming means may have a conical or pyramidal projection provided integrally on the one end face of the at least one punch body facing the through hole of the die.

The through hole of the die may have a polygonal shape including a triangular shape, an elliptical shape, an oval shape, or a closed curve shape. In this case, the punch body means may have at least one punch body having an outer configuration of a circular or quadrangular shape.

A method of forming a through hole in a sheet metal by the sheet metal punching apparatus according to any one of the above-described aspects is characterized by comprising the steps of: forming the pierced hole in the sheet metal by the pierced hole forming means; inserting the punch body means into the through hole of the die in a state in which the movement of the sheet metal is restricted by the pierced hole forming means inserted in the pierced hole; subjecting the sheet metal to tensile fracture at the outer edge of the through hole of the die through cooperation between the die and the punch body means, to thereby form the through hole in the sheet metal.

Advantages of the Invention

According to the present invention, it is possible to provide a sheet metal punching apparatus and a method thereof which make it possible to effect punching of a through hole of a special configuration other than the circular shape without using a punch whose outer configuration is similar thereto, thereby making it possible to attain a reduction in the punching cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a preferred embodiment of the present invention;

FIG. 2 is an explanatory enlarged side view of punch bodies and projections used in the embodiment shown in FIG. 1;

FIG. 3 is an explanatory front elevational view of a proximal portion, the punch bodies, and the projections used in the embodiment shown in FIG. 1;

FIG. 4 is an explanatory diagram of the punch bodies, the projections, and the die used in the embodiment shown in FIG. 1;

FIG. 5 is a diagram explaining the operation of the embodiment shown in FIG. 1;

FIG. 6 is a diagram explaining the operation of the embodiment shown in FIG. 1;

FIG. 7 is an explanatory partial cross-sectional view of another preferred embodiment of the present invention;

FIG. 8 is an explanatory partial cross-sectional view of still another preferred embodiment of the present invention;

FIG. 9 is an explanatory partial cross-sectional view of a further preferred embodiment of the present invention;

FIG. 10 is an explanatory partial cross-sectional view of a still further preferred embodiment of the present invention; and

FIG. 11 is an explanatory partial cross-sectional view of a further preferred embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereafter, a more detailed description will be given of the mode for carrying out the present invention on the basis of the preferred embodiments illustrated in the drawings. It should be noted that the present invention is not limited to these embodiments.

In FIGS. 1 to 4, a sheet metal punching apparatus 1 in accordance with this embodiment includes an upper die holder 2 which is raised and lowered by a hydraulic ram and the like; a pressing plate 3 secured to the upper die holder 2; a pressing pad 5 suspended from the upper die holder 2 through a resilient member 4; a punch holder 7 secured to the pressing pad 5 by means of a bolt 6 and the like and constructed as a punch unit; a lower die 9 on which a sheet metal 8 to be subjected to punching is placed; and a die 11 embedded in the lower die 9 and having a though hole 10 of an oval shape conforming to the shape of a through hole to be punched in the sheet metal 8, i.e., an oval shape in this embodiment.

The punch holder 7 includes a hollow cylindrical case 12 secured to the pressing pad 5 by means of the bolt 6 and the like; a hollow cylindrical slider 13 fitted to the case 12 vertically slidably; a punch means 14 fitted in the slider 13 vertically slidably; a returning means 16 disposed in the slider 13 and having the punch means 14 and a coil spring 15 for returning the punch means 14 and the slider 13 to their initial positions by upwardly resiliently urging the slider 13 by means of the punch means 14; and a slide guiding member 17 provided in the case 12 so as to guide the vertical movement of the punch means 14.

The die 11 has, in addition to the through hole 10, an oval through hole 19 which is continuous with the through hole 10, has a shape similar to but greater in size than the through hole 10, and is adapted to discharge punch waste 18 (see FIG. 6).

The slider 13 has a recess 21 on its circumferential surface, and is adapted to engage at the recess 21 a detent pin 22 secured to the case 12, so that the slider 13 does not come off the case 12 by the resiliency of the coil spring 15. The slider 13 is adapted to be pressed downward by the pressing plate 3 when the upper die holder 2 is lowered.

The punch means 14 for punching the sheet metal 8 includes a columnar proximal portion 25; a punch body means 28 which is provided on a circular lower end surface 26 of the proximal portion 25, has an outer configuration dissimilar to the configuration of an outer edge 27 of the oval through hole 10 of the die 11, and is adapted to form a through hole in the sheet metal 8 in cooperation with the die 11; a pierced hole forming means 31 which is integrally provided on one end face 29 of the punch body means 28 facing the through hole 10 of the die 11 and is adapted to form a pierced hole 30 (see FIG. 5) in the sheet metal 8 in cooperation with the die 11; and a collar portion 33 which is integrally provided on a circular upper end surface 32 of the proximal portion 25.

The punch body means 28 has at least one, in this embodiment three, columnar punch bodies 41 each of which has a circular outer configuration dissimilar to the configuration of the outer edge 27 of the oval through hole 10 of the die 11, and is inserted into the through hole 10. Each of the punch bodies 41 which are formed in the same configuration each other is secured at its upper end to the circular lower end surface 26 of the proximal portion 25 integrally or preferably detachably by means of bolts or fitting in order to be replaceable.

If the thickness of the sheet metal 8 is assumed to be t, each of the three punch bodies 41 is formed with an outside diameter which causes a minimal clearance 42 of not less than 0.15 t and not more than 2 mm to be created with respect to the outer edge 27 of the through hole 10 of the die 11. The three punch bodies 41 are arranged in a row in the longitudinal direction of the through hole 10, and a clearance 40 of such a measure that a tensile fracture along the outer edge 27 at the time of punching occurs in the sheet metal 8 is also provided between adjacent ones of the punch bodies 41.

The pierced hole forming means 31 has a conical or pyramidal (in this embodiment, conical) projection 43 provided integrally on the one circular end face 29 of each punch body 41 facing the through hole 10 of the die 11, and is adapted to form the pierced hole 30 in the sheet metal 8 by the projection 43 in cooperation with the die 11.

The coil spring 15 abuts against the collar portion 33 at one end thereof and a flange portion 45 of the slide guiding member 17 at the other end thereof. The slide guiding member 17 has, in addition to the flange portion 45, a cylindrical portion 47 formed integrally with the flange portion 45 and fitted in the case 12 in each hole 46 of the case 12, and slidably guides and supports at the inner peripheral surface of each cylindrical portion 47 each punch body 41 of the punch body means 28 inserted in each cylindrical portion 47.

In the above-described punching apparatus 1, as the pressing plate 3, the pressing pad 5, and the punch holder 7 are lowered in conjunction with the lowering of the upper die holder 2, the sheet metal 8 placed on the lower die 9 is pressed by the pressing pad 5 and is fixed by being clamped between the lower die 9 and the pressing pad 5. At the same time, the slider 13 is pressed by the pressing plate 3, and the punch means 14 is lowered in conjunction with the lowering of the slider 13. As the punch means 14 is lowered, the pierced holes 30 are formed in the sheet metal 8 by the projections 43 of the pierced hole forming means 31, as shown in FIG. 5. In the state in which the movement of the sheet metal 8 is restricted by the projections 43 of the pierced hole forming means 31 inserted in the pierced holes 30, the punch means 14 is lowered, and the punch bodies 41 of the punch body means 28 are inserted into the through hole 10 of the die 11. Thereupon, the sheet metal 8 is subjected to tensile fracture at the outer edge 27 of the through hole 10 of the die 11 through cooperation between the die 11 and the punch bodies 41 of the punch body means 28 as shown in FIG. 6, to thereby form an oval through hole 48 in the sheet metal 8.

Incidentally, according to the punching apparatus 1, the pierced holes 30 are formed in the sheet metal 8 by the pierced hole forming means 31, and in the state in which the movement of the sheet metal 8 is restricted by the pierced hole forming means 31 inserted in the pierced holes 30, the punch body means 28 having a circular outer configuration dissimilar to the configuration of the outer edge 27 of the oval through hole 10 of the die 11 is inserted into the through hole 10 of the die 11. Thereupon, the sheet metal 8 is subjected to tensile fracture at the outer edge 27 of the through hole 10 of the die 11 through cooperation between the die 11 and the punch body means 28, to thereby form in the sheet metal 8 the through hole 48 of the configuration conforming to the through hole 10. Therefore, it is possible to effect punching by using the punch bodies 41 whose outer configuration is circular in shape without using a punch whose outer configuration is similar to that of the through hole 48 to be punched, thereby making it possible to attain a reduction in the punching cost.

With the punching apparatus 1, the through hole 48 is formed by vertically moving the punch means 14, but the through hole 48 may be formed in an inclined portion of the sheet metal 8 by obliquely moving the punch means 14.

The above-described punching apparatus 1 is an example in which the punch body means 28 having three punch bodies 41 with a circular outer configuration dissimilar to the configuration of the outer edge 27 of the oval-shaped through hole 10 of the die 11 is used in order to form in the sheet metal 8 the through hole 48 conforming to the configuration of the outer edge 27 of the oval through hole 10 of the die 11. Alternatively, as shown in FIG. 7, in order to form in the sheet metal 8 the through hole 48 conforming to the configuration of the outer edge 27 of a substantially octagonal through hole 10 of the die 11, it is possible to use the punch body means 28 having one punch body 41 with a circular outer configuration dissimilar to the configuration of the outer edge 27 of the substantially octagonal through hole 10 of the die 11, as well as the pierced hole forming means 31 having the conical projection 43 provided integrally on the one end face 29 of one punch body 41 facing the through hole 10 of the die 11. Still alternatively, as shown in FIG. 8, in order to form in the sheet metal 8 the through hole 48 conforming to the configuration of the outer edge 27 of the through hole 10 of the die 11, the through hole 10 having a configuration in which an elliptical shape and a quadrangular shape continuous to the elliptical shape are combined, it is possible to use the punch body means 28 having two punch bodies 41 respectively provided with large and small circular outer configurations dissimilar to the configuration of the outer edge 27 of the through hole 10 of the die 11, as well as the pierced hole forming means 31 having the conical projection 43 provided integrally on the one end face 29 of each punch body 41 facing the through hole 10 of the die 11. Still more alternatively, as shown in FIG. 9, in order to form in the sheet metal 8 the through hole 48 conforming to the configuration of the outer edge 27 of the through hole 10 of the die 11, the through hole 10 having the configuration of a closed curve, it is possible to use the punch body means 28 having one punch body 41 with a circular outer configuration dissimilar to the configuration of the outer edge 27 of the through hole 10 of the die 11, as well as the pierced hole forming means 31 having the conical projection 43 provided integrally on the one end face 29 of the punch body 41 facing the through hole 10 of the die 11. Still more alternatively, as shown in FIG. 10, in order to form in the sheet metal 8 the through hole 48 conforming to the configuration of the outer edge 27 of the through hole 10 of the die 11, the through hole 10 having the configuration of a closed curve, it is possible to use the punch body means 28 having one punch body 41 with a quadrangular outer configuration dissimilar to the configuration of the outer edge 27 of the through hole 10 of the die 11, as well as the pierced hole forming means 31 having the conical projection 43 provided integrally on the one end face 29 of the punch body 41 facing the through hole 10 of the die 11.

Additionally, in the above, the through hole 48 is formed in the sheet metal 8 by subjecting the sheet metal 8 to tensile fracture over the entire region of the outer edge 27 of the through hole 10 of the die 11. However, as shown in FIG. 11, in order to form in the sheet metal 8 the through hole 48 conforming to the configuration of the outer edge 27 of the through hole 10 by shearing in regions 51 and by tensile fracture in regions 52 excluding the regions 51 at the outer edge 27 of the through hole 10 of the die 11, the through hole 10 having the configuration of a closed curve, it is possible to use the punch body means 28 having one punch body 41 with outer configuration partially similar to, and outer configurations partially dissimilar to, the configuration of the outer edge 27 of the through hole 10 of the die 11, as well as the pierced hole forming means 31 having the conical projection 43 provided integrally on the one end face 29 of the punch body 41 facing the through hole 10 of the die 11.

Furthermore, although, in the above, the conical projection 43 is used, it is alternatively possible to use a projection 43 of a polygonal pyramid shape including a triangular pyramid shape, or a projection 43 in which a cylindrical body or a prismatic body is disposed on the proximal portion 25 side while a conical body or a pyramidal body is disposed on the distal end side, and the cylindrical body or the prismatic body is formed integrally with the conical body or the pyramidal body. In addition, in the present invention, if the thickness of the sheet metal is assumed to be t, it suffices if the clearance 42 between the punch body and the outer edge of the through hole of the die is between 0.1 t to 20 t. Additionally, the die 11 itself may be used as the lower die without using the lower die 9 in which the die 11 is embedded. 

1. A sheet metal punching apparatus comprising: a die having a through hole of a configuration conforming to a configuration of a through hole to be formed in a sheet metal; and a punch means including a punch body means having an outer configuration dissimilar to a configuration of an outer edge of the through hole of said die and adapted to form a through hole in the sheet metal in cooperation with said die and a pierced hole forming means which is integrally provided on one end face of said punch body means facing the through hole of said die and is adapted to form a pierced hole in the sheet metal, wherein the pierced hole is formed in the sheet metal by said pierced hole forming means, and in a state in which the movement of the sheet metal is restricted by said pierced hole forming means inserted in the pierced hole, said punch body means is inserted into the through hole of said die, whereby the sheet metal is subjected to tensile fracture at the outer edge of the through hole of said die through cooperation between said die and said punch body means, to thereby form the through hole in the sheet metal.
 2. The sheet metal punching apparatus according to claim 1, wherein said punch body means has at least one punch body having an outer configuration dissimilar to the configuration of the outer edge of the through hole of said die, and said pierced hole forming means has a conical or pyramidal projection provided integrally on the one end face of said at least one punch body facing the through hole of said die.
 3. The sheet metal punching apparatus according to claim 1, wherein the through hole of said die has a polygonal shape including a triangular shape, an elliptical shape, an oval shape, or a closed curve shape, and said punch body means has at least one punch body having an outer configuration of a circular or quadrangular shape.
 4. A method of forming a through hole in a sheet metal by the sheet metal punching apparatus according to claim 1, comprising the steps of: forming the pierced hole in the sheet metal by said pierced hole forming means; inserting said punch body means into the through hole of said die in a state in which the movement of the sheet metal is restricted by said pierced hole forming means inserted in the pierced hole; subjecting the sheet metal to tensile fracture at the outer edge of the through hole of said die through cooperation between said die and said punch body means, to thereby form the through hole in the sheet metal. 